National currencies are the official money used by a country for transactions, trade, and economic activities. Each country typically has its own currency, which is issued and regulated by a central bank. For example, the United States uses the U.S. Dollar, while Japan uses the Yen. These currencies can vary in value and are often exchanged in the global market. The value of a currency can be influenced by factors such as inflation, interest rates, and economic stability. Countries may also participate in currency unions, like the Eurozone, where multiple nations share a common currency, the Euro.